/*
 * Copyright (C) 2014 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
import static com.google.common.util.concurrent.MoreExecutors.newDirectExecutorService;

import com.google.caliper.AfterExperiment;
import com.google.caliper.BeforeExperiment;
import com.google.caliper.Benchmark;
import com.google.caliper.Param;
import com.google.caliper.api.Footprint;
import com.google.caliper.api.VmOptions;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.Executor;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * A benchmark comparing the {@link MoreExecutors#newDirectExecutorService()} to
 * {@link MoreExecutors#directExecutor}.
 */
@VmOptions({"-Xms12g", "-Xmx12g", "-d64"})
public class MoreExecutorsDirectExecutorBenchmark {
    enum Impl {
        EXECUTOR_SERVICE {
            @Override
            Executor executor() {
                return newDirectExecutorService();
            }
        },
        EXECUTOR {
            @Override
            Executor executor() {
                return directExecutor();
            }
        };
        abstract Executor executor();
    }

    @Param
    Impl impl;
    Executor executor;

    static final class CountingRunnable implements Runnable {
        AtomicInteger integer = new AtomicInteger();

        @Override
        public void run() {
            integer.incrementAndGet();
        }
    }

    CountingRunnable countingRunnable = new CountingRunnable();

    Set<Thread> threads = new HashSet<Thread>();

    @BeforeExperiment
    void before() {
        executor = impl.executor();
        for (int i = 0; i < 4; i++) {
            Thread thread = new Thread() {
                @Override
                public void run() {
                    CountingRunnable localRunnable = new CountingRunnable();
                    while (!isInterrupted()) {
                        executor.execute(localRunnable);
                    }
                    countingRunnable.integer.addAndGet(localRunnable.integer.get());
                }
            };
            threads.add(thread);
        }
    }

    @AfterExperiment
    void after() {
        for (Thread thread : threads) {
            thread.interrupt(); // try to get them to exit
        }
        threads.clear();
    }

    @Footprint
    Object measureSize() {
        return executor;
    }

    @Benchmark
    int timeUncontendedExecute(int reps) {
        final Executor executor = this.executor;
        final CountingRunnable countingRunnable = this.countingRunnable;
        for (int i = 0; i < reps; i++) {
            executor.execute(countingRunnable);
        }
        return countingRunnable.integer.get();
    }

    @Benchmark
    int timeContendedExecute(int reps) {
        final Executor executor = this.executor;
        for (Thread thread : threads) {
            if (!thread.isAlive()) {
                thread.start();
            }
        }
        final CountingRunnable countingRunnable = this.countingRunnable;
        for (int i = 0; i < reps; i++) {
            executor.execute(countingRunnable);
        }
        return countingRunnable.integer.get();
    }
}
